Steam superheater



A. PARSONS ANDS. S. COOK.-

Y STEAM SUPERHAATER.

APPLICATION FILED JUNE 26,1918,

Patented July 4, 1922.

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APPLICATION FILED JUNE 26, I9I.

Patented July 4, 1922.

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STEAM SUPERHEATER.

APPLICATION FILED JUNE 26, 1918.

Patented July 4, 1922;-

3 SHEETS-SHEET 3.

03W PNA www m. mi fm@ nn ma Q5@ CHARLES ALGERNON PARSONS ANDSTANLEY SMITH (300Ky OF WALLSEND-ON-TYNE, l ENGLAND; SAID COOK ASSIGNOR TO SAID PARSONS.4

STEAM SUPERHEATER.

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Specication of Letters Patent.

Patented July t, 11922;.

@riginal application filed ltpril 27, 1917, Serial No. 165,048. Divided and this application, filed. June 26,

' i 1918 Serial No. 2423105.

To all whom 2' 1f may concern, A

Be'itdmoyvn that we7 CHARLES ALennNoN Passons and STANLEY SMITH Coon7 .both subjects of thelI-ing of Great Britain and lrelanch and both residing at Turbinia `lllorhs, `Wallsendon-Tyne, in the county o f Northumberland, England, have invented certain new and useful lmprovements in and Relating to Steam Superheaters, of which the following a specification.

The present invention relates to improvements in steam superheaters.

As ordinarily constructed, superheaters consist of tubes or chambers so disposed as to be exposed externally to the flames or hot gases of combustion, and so connected that the steam passes through them on its passage from the boiler to the engine, whereby the steam is increased in temperature by the desired amount.

Difficulty has been experienced in theoperation of such plants throughvtlie superheater acquiring an excessive. temperature When the-demand for steaml either ceases or is reduced. This difficulty is particularly serious when the utilization of steam is only temporarily suspended, as under such cir cumstances when the regulating valves are again opened, the very high temperature steam from the superheater is liable to cause considerable damage to the engine parts.

These dangers are not in any way overcome by the fact that the boiler is provided with safety valves, because, although surplus steam generated in the boiler by excessive heat in the furnaces will blow offfthrough the relief valves as the pressure increases, no passage of fresh steam takes place through the superheater, which therefore continues to rise in tempera-ture.

The object of the present invention is to provide automatic means for preventing excessive heating of the superheater tubes, when the ordinary consumption of steam is reduced or ceases by regulating or closing down the regulating valves in the steam supply pipes.

The invention consists in means for preventing overheating in steam superheaters comprising a superheater safety valve with means for varying the bloW-ofll pressure of such valve controlled by the temperature in a superheater tube or in the neighbourhood of the superheater tube.

The invention further. consists inthe improved constructionsof superheaters hereinT inaftel' described.

Referring tothe accompanying drawings Figure l shoivs a superheater safetyvalve with means for causing the blowoifipresure to b e influenced by the temperature ofthe steam in the superheater.,

Figure 2 shows a modified` form in'which an Vincrease in the temperature ofv the; steam above a certain degree positively causes the superheater safety valveto lift;

Figure Sis vertical section showing a form of theinvention in which therbloir-off pressure of the safety valve depends upon the temperature of the gases surrounding the superheater.

Figurea being a part plan ofthe same.

Figure 5 is a modification of theform shownin Figure 2.

In the forni of the invention. shown in Figure l, the safety valverl andA its gear are mounted on a casting 2. An enlarged lsuperheater tube 3 in series with onerof the ordi nary coils 4 of the superlieater is also rigidly attached to the casting Q. This tube contains a. thermostat consisting of a seriesof concentric tubes 5, 6, which. are alternately of steel and of a special alloy which has a high coetlicient of expansion with increasing temperature. As these tubes are arranged alternately a considerablecumulative differential expansion is obtained between the outermost of the steel tubes and the central bar T, and any increase of temperature thereforegcauses,thebar to project further through the casting Q. The collar S on the bar 7 is in contact with the bell crank lever 9 which transmits the movement of the bar 'T to the spring cap 'l0 on the safety valve. The initial kcompression ofthe safety valve spring under normal Working conditions-keeps the bell crank lever 9 and the collar 8 in Contact, and any increase in temperature of the steam in the superheater tube 3 causes the safety valve spring cap 10 to .lift and'so reduces the spring compression and thebloW-off pressure ofthe valve.

ln order toy avoid a large compression of the safety valve spring when theboilers are shut down and allowed to cool heavy springll with a very-small compression and` an adjusting handi Wheel nut lmay be provided on the end of the bar 7. This spring takes up the further movement of the bar after the lever 13 has come into contact with the safety valve cover 14. The hand wheel nut 12 may also be used (Whether the spring 11 is fitted or omitted) for adjusting theblovwoff pressure in addition to the adjustment obtained by the ordinary nut 15.

It Will be noticed that the sleeve 16 through Which the end of the nut 15 screws, and which is carried on the end of the lever 13,'is free to slide vertically, being constrained only by the lever 13.

In the-modified form of the invention shown in Figure 2, the lever 13 operates the safety valve stem 17 itself instead of operating the safety valve spring cap. In this case an increase in temperature in the superheater tube causes the safety valve to be positively lifted.

In the modification shown in Figures 3 and 4,y the thermostat 21 is placed in the uptake adjacent to the superheater tubes 22 so that the differential expansion depends upon the temperature of the gases surrounding the superheater. The relay valve 23 is provided With a spring 24 sufficient to keep the valve closed against the steam pressure. A slight expansion of the bar 25 above a predetermined amount will cause the relay valve to lift by the movement of the lever 26, and thereby admits steam yby thepipe 27 tothe chamber 28 in the safety valve 29. TheV steam. pressure in the chamber 28 acts upon the annular surface 30, thus opposing the safety valve spring 31 and reducing the Ablow-off pressure of the valve. In this modification the thermostat. consists of a fiat bar 32 of special alloy riveted at one end to the free end of a double vbar 33, 34, which is slidably supported on a bracket 36. The other end of the bar 33 is rigidly attached to Vthebase of the relay valve 23, so that the differential expansion of these bars causes the bar v32 to project further through the uptake the lift the lever 26 and valve 23.

It will be seen that the thermostatsmay be interchanged, either type being used in any of the examples illustrated. It will also be seen that in either type of thermostat any number of pairs may be utilized to obtain the required amount of movement by differential expansion. i 'n l j ln the modification of the'invention shown in Figure 5, the safety valve is provided with two springs 40, 41, which have a double cap connecting` piece 42. The lever 13 operates the latter,causing it to be lifted when the Y influencing temperature increases. Under normal Working conditions the adjusting screw 43 is set so as to bring the lever 9 into contact With the end of the bar y7 While theconnecting piece 42 is'in a free position, the springs 40, 41, being then equally stressed. When the connecting piece 42 is lifted by the lever 13 the spring 40 is further pressed, but the spring 41 has its compression reduced so that the blow-off 'pressure is correspondingly reduced.

t Will be seen that the lever and link transmission gear is not under stress until abnormally high temperatures prevail. The` springs 40, 41, need notbe of the length shown in the drawing and the spring 40 may conveniently be made much shorter than the spring 41. i l

Vhere in the appended claims I refer to the temperature associated With the superheater these terms are used in a generic sense to include means located in the superheater or located in such relation thereto as to be affected by the changes in temperature corresponding substantially to the changes which take place in the superheater.

Having now described our invention, what We claim as new and desire to secure by Letters Patent is 1. In combination with a steam superheater for steam boilers, a relief valve controlling the exit of steam from the superA heater and operating means for said valve, including a thermostat associated with said superheater and having control of said valve to cause it to blow off steam proportionally to the rise in temperature of said superheater consequent upon the demand for steam being reduced or ceasing.

2. ln combination With a steam superheater for steam boilers, a relief valve controlling the exit of steam from the superheater, a thermostat associated With said superheater, and means for controlling said valve from said thermostat, whereby the valve will blowV off when the temperature rises Within the superheater, consequent upon the demand for steam being reduced or ceasing. y Y

y3. Incombination with a steam superheater for steam boilers, a relief valve Vcontrolling the exit of steam from the super- Y heater a thermostat associated with the superheater, means v for exerting pressure upon saidvalve against its opening movement and means operated by the thermostat to decrease the pressure of said pressure means uponvithe valve to permit it to open Vprogressively with increase of temperature admit steam tosaid piston so controlled by said thermostat that increase of temperature in the superheater causes decrease in blowing-oiln pressure of said relief valve, substantially as described.

5. In combination with a steam superheater, a blow off Valve for the superheater,

5 and thermostatc controlling means associated with the superheater end operating to open said valve when the temperature in the superheater uses to a predetermined CHARLES ALGERNON PARSDNS. STANLEY SMITH CK. 

